It appears that you want to search a "C" program for the declaration of the variable specified by $ur. Before you even consider regular expressions, you should look for a module to do this, especially if you have to parse the declaration after you find it.

I can offer a few comments on the regexes you have shown.

You are matching a multi-line string. They probably all should use both the /m and /s modifiers.

$reg1 and $reg2 are largely redundant. Any string that fails 1 will also fail 2. Any string that matches 2 will also match 1.

In your example, $reg3 and $reg5 match exactly the same thing.

Variables declared with qr can potentially speed your program if they are declared outside the loop where they are used because they are only complied once.